Contamination resistant insulator

ABSTRACT

A contamination resistant insulator including an insulative body having a heating resistor provided therein which emits heat to evaporate moisture deposits on the insulator. A humidistat means is mounted on the exterior surface of the insulative body and is adapted to energize and close a coil operated switch means upon sensing a predetermined humidity level. The switch means, upon being activated and closed, short circuits a switching resistor which is series connected to the heating resistor to increase the current flow in the heating resistor to increase the amount of heat generated thereby. A thermocouple is provided in the resistor circuit to deenergize and open the switch means upon the temperature of the insulator reaching a predetermined level. The opening of the switch means causes the current flow in the heating resistor to be lowered due to a circuit being reestablished through the switching resistor.

United States Patent [72] Inventor Essam Nas'er Ames, Iowa [21 Appl. No. 887,263 [22] Filed Dec. 22, 1969 [45] Patented June 15, 1971 [7 3] Assignee Iowa State University Research Foundation Ames, Iowa [54] CONTAMINATION RESISTANT INSULATOR 7 Claims, 3 Drawing Figs. [52] 11.8. 219/209, 219/201, 219/213 [51] Int. Cl H05b l/00 [50] Field of Search 219/200, 201, 203, 204, 213, 522; 340/334, 235; 236/3, 44 C; ZOO/61.04, 61.06

[56] References Cited UNITED STATES PATENTS 1,856,124 5/1932 Austin 219/209 2,662,156 12/1953 Potter 219/209 3,526,753 9/1970 Aisanichetal.

Primary Examiner-R. F. Staubly Assistant Examiner-C. L. Albritton Attorney-Zarley, McKee and Thomte ABSTRACT: A contamination resistant insulator including an the heating resistor to increase the current flow in the heating resistor to increase the amount of heat generated thereby. A thermocouple is provided in the resistor circuit to deenergize and open the switch means upon the temperature of the insulator reaching a predetermined level. The opening of the switch means causes the current flow in the heating resistor to be lowered due to a circuit being reestablished through the switching resistor.

, CONTAMINATION RESISTANT INSULA'IOR Electrical insulators frequently become contaminated with natural and/or artificial deposits from the air and these deposits readily absorb moisture naturally occurring in the air such as fog, dew, drizzle, rain or combinations thereof. The absorption ofthe moisture by the contamination layer causes the layer to become highly conductive and often carries current from the power line to ground. The above condition can lead to the formation of an are which bridges the insulator and which causesa short circuit at this point with possible permanent damage to the insulator. Additionally, the short circuit creates a disturbance to the remainder of the system and must be avoided at all costs. The switching off" of this line may be undesirable and may cause other lines to become overloaded.

Some attempt has been made previously to heat the insulator to evaporate the moisture deposits but such attempts have been unsatisfactory due to the economic considerations thereof. Further, the previous attempts to evaporate the moisture on the insulators were also unsatisfactory due to the unreliability thereof.

Therefore, it is a principal object of this invention to provide a contamination resistant insulator.

A further object of this invention is to provide acontamination resistant insulator which is economical of manufacture.

A still further object of this invention is to provide a contamination resistant insulator which is sufficient in operation.

A further object of this invention is to provide a contamination resistant insulator which efficiently and economically evaporates all moisture deposits thereon.

A still further object of this invention is to provide a contamination resistant insulator including a switching resistor and a heating resistor, the switching resistor providing efficient switching of high voltages encountered in some applications.

A still further object of this invention is to provide a contamination resistant insulator which includes a thermocouple operatively connected to. a heating resistor which protects the insulator from becoming overheated and which reduces the amount of lost energy. A still further object of this invention is to provide a contamination resistant insulator which prevents the arcing thereof and which eliminates undesirable short circuits.

These and other objects will be apparent to those skilled in the art.

This invention consists in the construction, arrangements, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings in which:

FIG. I is a schematic view of the electrical circuitry of the insulator of this invention;

FIG. 2 is a fragmentary longitudinal sectional view of the insulator wherein heating energy is provided from a high voltage line; and

FIG. 3 is, a fragmentary longitudinal sectional view of a modified form of the insulator wherein heating energy is provided from a 1 15 volt alternating current source.

The numeral 10 generally refers to a lead connected to a suitable source of electrical energy such as l 15 volts AC (FIG.3) or a high voltage line (FIG. 2) while the numeral 12 refers to a suitable ground. FIG. 2 illustrates the form of the insulator when heating energy is supplied from a high voltage line while FIG. 3 illustrates the form of the insulator when heating energy is supplied from a l 15 volt alternating current source. Inasmuch as the structure of FIG. 3 is substantially identical to the structure of FIG. 2, only FIG. 2 will be described in detail with identical structure in in FIG. 3 being indicated by A heating resistor 14 is connected to ground 12 by a lead 16 and a lead 18, which in the embodiment of FIG. 3 must be adequately insulated, connects resistor 14 with a switching resistor 20 which is connected to lead 10.

Lead 16 is connected to a contact 22 of a thermo-humiditymeter means 24 (conventional humidistat-thermostat) by a lead 26. Lead 26 when employed in configuration of FIG. 2 must be adequately insulated. The other contact 28 of means 24 is connected to contact 30 of switch 29 by a lead 32. Means 24 is normally open but will become closed when exposed to a. predetermined humidity level. Switch 29 also includes contacts 34, 36 and 38. Lead 40 is connected. to contact 36 and is connected to lead 10 at 42. Lead 44 is connected to contact 38 and is connected to lead 18 at 46. Contact 34 is connected to contact 48 of a normally closed thermocouple 50 by lead. 52. Contact 54 of thermocouple 50 is connected to lead 26 by a lead 54 at 56.

Switch 29 is coil operated and the coil thereof is generally designated by the reference numeral 58. Coil 58 is connected to lead 10 at 60 by lead 62. Coil 58 is connected to lead 32 at 64 by lead 66. When coil-58 is energized, plunger 67 is moved to the right (as viewed in FIG. 1) to cause the contacts 36 and 38 to be electrically connected and to cause the contacts 50 is normally closed and it is preferred that the thermocouple opens at a predetermined temperature such as 70 C. As seen in FIG. I, a high-ohmic resistor 69 is imposed in lead 71 which extends between leads 26 and 32. Resistor 69 is optional structure on the device of this invention.

The components of FIG. 1 are positioned in a power system insulator generally designated by the reference numeral 68. Insulator 68 includes a hollow body portion 70 having a plurality of sheds 72 extending outwardly therefrom. Insulator 68 includes a base portion 74 through which the lead 16 extends. Resistor 14 is designed so as to be positioned close to the interior wall surface 76 of body portion 70 to insure that the body portion 70 will receive substantially all of the heat generated by resistor 14. Thermocouple 50 is placed adjacent the wall surface 76 to permit it to sense the temperature of body portion 70. The numeral 78 refers to a housing provided at one end of insulator 68 in which certain components are housed. Preferably, the thermo-humidity-meter 24 is mounted on the exteriorsurface of housing 78 to permit it to properly sense humidity conditions. In FIG. 3 it can be seen that the components have been arranged somewhat differently than that of FIG. 2, with the primary differences being in the reversal of the positions of elements 74' and 78' and the structure associated therewith. The embodiments of FIGS. 2 and 3 function identically.

The operation of the insulator and its associated circuitry is as follows. The insulator is placed in its desired environment and electrical energy furnished thereto either from the high voltage line (FIG. 2) or a volt alternating current source (FIG. 3). The means 24 is normally open and will remain open until it senses a predetermined amount of humidity at which time it will close. Thermocouple 50 is normally closed'and will remain so until the insulator body reaches a predetermined temperature. Initially, a circuit will be established through lead 10, resistor 20, lead 18, resistor 14, lead 16 and ground 12. The resistor 14 will generate a certain amount of heat when the above-described circuit is functioning thereby causing a certain amount of moisture to be evaporated from the insulator. When the humidistat 24 senses the predetermined humidity level, (for example during periods of rain, fog, etc.), the coil 58 will be energized and a circuit will be created through lead 10, lead 62, coil 58, 64, lead 32, contacts 28 and 22, lead 26, lead 16 and ground 12. The energization of coil 58 causes contacts 36 and 38 to be electrically connected and also causes contacts 30 and 34 to be electrically connected. The closing of switch 29 causes the resistor 20 to be bypassed or short circuited which results in more current flowing through resistor 14 which results in additional heat being generated thereby within insulator 68 to evaporate the humidity therefrom. If humidistat 24 should open, the additional current flowing through resistor 14 will continue since a circuit will exist through lead 10, lead 62, coil 58, 64, lead32, contacts 30 and 34, lead 52, thermocouple 50, lead 54, 56, lead 26, lead 16, ground 12, resistor 14, lead 18, 46, lead 44,

contacts 38 and 36, lead 40 and 42. Thus, the heating process will continue until thermocouple 50 opens upon the temperature of the insulator body reaching the predetermined level which would usually be approximately 70 C. When thermocouple 50 opens, the circuit through both of the resistors 20 and 14 will again be established with the result that resistor 14 will emit less heat than during the time coil 58 was encrgized which reduces'the amount of energy used to evaporate the moisture from the insulator and thereby improve the economy of the delay.

The resistor 20 serves to efficiently switch the high voltages that may be encountered in some applications and thereby prolongs the life of contacts 36 and 38. The thermocouple 50 protects the insulator from becoming over heated and also reduces the amount of energy lost in the process thereby improving the economy of the delay. The insulator described herein insures that all moisture deposits will be evaporated from the insulator to prevent an arc from bridging the insulator which could cause an undesirable short circuit and which could also damage the insulator. Thus, the insulator described herein prevents short circuits and damage to the insulator and also prevents a disturbance in the system. The moisture is evaporated from the insulator in an efficient manner with a minimum amount of energy. Thus it can be seen that the device accomplishes at least all of its stated objectives. Some changes may be made in the construction and arrangement of my Contamination Resistant insulator without departing from the real spirit and purpose of my invention,'and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

lclaim:

I. An electrical insulator, comprising,

a hollow body portion having interior and exterior surfaces,

a heating resistor mounted in said hollow body portion electrically I connected to a source of electrical energy adapted to emit heat when energized and adapted to transfer said heat to said body portion,

a switching resistor series connected to said power source and said heating resistor,

a normally open switch means electrically connected to said switching resistor for deenergizing said switching resistor when moved to its closed position,

a normally open humidistat means electrically connected .to said power source and said switch means, said humidistat means closing said switch means upon a predetermined humidity condition being senses thereby,

said heating resistor having an increased current flow therethrough upon said humidistat means closing saidswitch means and deenergizing said switching resistor,

said increased current flow in said heating resistor causing additional heat to be furnished to said body portion to evaporate moisture thereon,

and a normally closed thermocouple means electrically connected to said switch means adapted to open said switch means upon said body portion reaching a predetemtined temperature.

2. The insulator of claim 1 wherein said humidistat means is mounted on the exterior surface of said body portion.

3. The insulator of claim 1 wherein said thermocouple means is mounted in said hollow body portionadjacent the interior wall thereof.

4. The insulator of claim' 1 wherein said heating resistor is positioned closely adjacent the interior wall surface of said body portion.

5. The insulator of claim 1 wherein said switch means is an electrical coil operated double pole switch means including first and second pairs of contacts, one of the contacts of said first pair of contacts being electrically connected to one side of said switching resistor, the other contact of said first pair of contacts being electrically connected to the other side of said switching resistor,'said switching resistor being short circuited upon said switch means bein closed.

6. The insulator of claim wherein one of the contacts of said second pair of contacts is electrically connected to one terminal side of said humidistat means, the other contact of said second pair of contacts being electrically connected to one terminal side of said thermocouple means, the other terminal side of said thermocouple means being electrically connected to a lead extending from ground to the other terminal side of said humidistat means.

7. The insulator of claim 1 wherein a first lead connects said power source to one end of said switching resistor, a second lead connecting one end of said switching resistor to one end of said heating resistor, a third lead connecting the other end of said heating resistor to ground, a fourth lead connecting said third lead to one contact of said humidistat means, said switch means including first and second pairs of contacts which are opened and closed by a coil means, a fifth lead connecting the other contact of said humidistat means with one contact of said second pair of contacts, a sixth lead connecting said first lead and one end of said coil means, a seventh lead connecting the other end of said coil means with said fifth lead, an eighth lead connecting the other contact of said second pair of contacts with said fourth lead, said thermocouple means being imposed in said eighth lead, a ninth lead connecting said first lead with one contact of said first pair of contacts, and a 10th lead connecting the other contact of said first pair of contacts with said second lead. 

1. An electrical insulator, comprising, a hollow body portion having interior and exterior surfaces, a heating resistor mounted in said hollow body portion electrically connected to a source of electrical energy adapted to emit heat when energized and adapted to transfer said heat to said body portion, a switching resistor series connected to said power source and said heating resistor, a normally open switch means electrically connected to said switching resistor for deenergizing said switching resistor when moved to its closed position, a normally open humidistat means electrically connected to said power source and said switch means, said humidistat means closing said switch means upon a predetermined humidity condition being senses thereby, said heating resistor having an increased current flow therethrough upon said humidistat means closing said switch means and deenergizing said switching resistor, said increased current flow in said heating resistor causing additional heat to be furnished to said body portion to evaporate moisture thereon, and a normally closed thermocouple means electrically connected to said switch means adapted to open said switch means upon said body portion reaching a predetermined temperature.
 2. The insulator of claim 1 wherein said humidistat means is mounted on the exterior surface of said body portion.
 3. The insulator of claim 1 wherein said thermocouple means is mounted in said hollow body portion adjacent the interior wall thereof.
 4. The insulator of claim 1 wherein said heating resistor is positioned closely adjacent the interior wall surface of said body portion.
 5. The insulator of claim 1 wherein said switch means is an electrical coil operated double pole switch means including first and second pairs of contacts, one of the contacts of said first pair of contacts being electrically connected to one side of said switching resistor, the other contact of said first pair of contacts being electrically connected to the other side of said switching resistor, said switching resistor being short circuited upon said switch means being closed.
 6. The insulator of claim 5 wherein one of the contacts of said second pair of contacts is electrically connected to one terminal side of said humidistat means, the other contact of said second pair of contacts being electrically connected to one terminal side of said thermocouple means, the other terminal side of said thermocouple means being electrically connected to a lead extending from ground to the other terminal side of said humidistat means.
 7. The insulator of claim 1 wherein a first lead connects said power source to one end of said switching resistor, a second lead connecting one end of said switching resistor to one end of said heating resistor, a third lead connecting the other end of said heating resistor to ground, a fourth lead connecting said third lead to one contact of said humidistat means, said switch means including first and second pairs of contacts which are opened and closed by a coil means, a fifth lead connecting the other contact of said humidistat means with one contact of said second pair of contacts, a sixth lead connecting said first lead and one end of said coil means, a seventh lead connecting the other end of said coil means with said fifth lead, an eighth lead connecting the other contact of said second pair of contacts with said fourth lead, said thermocouple means being imposed in said eighth lead, a ninth lead connecting said first lead with one contact of said first pair of contacts, and a 10th lead connecting the other contact of said first pair of contacts with said second lead. 